Selective photocatalytic aerobic oxidation of methane into carbon monoxide over Ag/AgCl@SiO2.

Design of active catalysts for chemical utilization of methane under mild conditions is of great importance, but remains a challenging task. Here, we prepared a Ag/AgCl with SiO2 coating (Ag/AgCl@SiO2) photocatalyst for methane oxidation to carbon monoxide. High carbon monoxide production (2.3 µmol h-1) and high selectivity (73%) were achieved. SiO2 plays a key role in the superior performance by increasing the lifetime of the photogenerated charge carriers. Based on a set of semi in situ infrared spectroscopy, electron paramagnetic resonance, and electronic property characterization studies, it is revealed that CH4 is effectively and selectively oxidized to CO by the in situ formation of singlet 1O2 via the key intermediate of COOH*. Further study showed that the Ag/AgCl@SiO2 catalyst could also drive valuable conversion using real sunlight under ambient conditions. As far we know, this is the first work on the application of SiO2 modified Ag/AgCl in the methane oxidation reaction.